2009 marzocchi 55 R issues

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2009 marzocchi 55 R issues
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flag turtlesauce2000
Posted: Sep 2, 2011 at 10:18 Quote
So, I bought some second hand 2009 marzocchi 55 R's off of ebay Smile
When they arrived tho i discovered that the rebound cartridge is locked Frown

I have done some googling and found out that marzocchi fixed this issue by drilling tiny holes in the bottom of the cartridge to convert it into a HSCV style damper. The only thing is, where and what size should these holes be?

If anyone has had the mod performed on their fork could you either give me some info or show me a picture of the mod on your cartridge.


Many thanks in advance Smile
flag kixx
Posted: Sep 3, 2011 at 15:43 Quote
ok ...... this is how you do it:

1. the cartridge has a threaded extension on the bottom that goes through the lower so you can screw on the retaining nut .... take that off and do your measurements starting just above the thread on the bottom of the cartridge (the nitrogen piston on the bottom is about 13 mm tall). drill a hole between 6 to 12 mm from the bottom of the cartridge (i drilled mine round 8mm). drill with a 2-2.5 mm drill straight trough the middle and onto the other side (nitrogen and oil will be gushing out ... just a little actually ....) cycle the rebound shaft and force it to the bottom. now lock the piston down with something (like a nail/screw/whatever ... if you can't see trough the other side, drill again but don't forget to extend the shaft so you don't damage the rebound valve) . i used a 2.5 mm nail and bent it at the end so it doesn't come out.

2. make sure the rebound shaft is fully extended out of the cartridge and drill two holes with a 2.5 mm bit on opposite sides of the cartridge at about 30 mm from the bottom. cycle any oil out (this will turn your cartridge into an open bath one).

3. the top of the cartridge (near the rebound shaft) has some indentations on it to keep the top of the sealing assembly from sliding down the cartridge. drill into one of those indentations with a 1 mm bit. be careful not to force the drill, or you'll scratch the shaft (it will go in about 2 mm). don't push on it too much after it went trough the shell, it's mostly aluminum inside so it will be easy to drill. once you feel like rock solid behind it, stop. (check with your mouth to see if you can pull air out ... if you can't, keep drilling ... but be careful). this way the air inside the cartridge will have a way to come out and allow oil to go up and fill the cartridge.

4. you're done with the drilling. thread back the extension on the bottom of the cartridge and assemble the fork back. now you need to use thicker oil to compensate for the holes in the bottom (i used 10w and it felt like new). fill the fork with oil until the level is just above the cartridge. cycle the shaft until all the air is out. complete oil.

5. beer Smile


and a side note: the cartridge is pressurized and helps the fork not bottom out. without the pressure from the cartridge (it acts as a second spring) you need to ramp up the air pressure, and the oil volume in the air chamber to compensate (for the lack of a bottom out). otherwise you'll just bottom out the forks with ease. take a syringe and 7.5 wt oil. pump up the air pressure until you have a correct sag. jump on the fork to see how much travel you get. if you bottom out, take all the air out and remove the schrader valve from the top cap. use the syringe to add 5ml of 7.5 wt oil (this makes the air chamber smaller and adds progressiveness to the fork and increases the bottom out part of the travel). install back the valve and fill with air. check the travel. if not satisfied, remove the valve and keep adding oil until you are ok with it. if you add too much, you can tilt the fork and use the syringe to pull oil out. no need to take the cap off Smile
flag turtlesauce2000
Posted: Sep 4, 2011 at 2:21 Quote
Cheers!

I dont get the bit at the beginning about removing the threaded extension.

After youve finished do you leave the nail in to hold the piston down?
flag kixx
Posted: Sep 4, 2011 at 9:16 Quote
the cartridge has an aluminum extension on the bottom that's threaded on:

http://i155.photobucket.com/albums/s281/flyag1/IMG_2617.jpg

the thingy at the bottom with a hexagonal profile ..... that's threaded on. vice grip the cartridge and use a wrench to take it off. or you can simply leave it on and start your measurements from where the cartridge bulge starts.

and yes .... the nail has to stay. it keeps the nitrogen piston inside the cartridge in place at the base so you don't get another hydro lock. the hydro lock appears when nitrogen and oil switch places and the piston moves up the cartridge (blocking the fork's travel). sometimes it happens that the fork remains stuck down (the nitrogen escapes the lower chamber and moves up in the cartridge).
flag turtlesauce2000
Posted: Sep 4, 2011 at 9:24 Quote
i did it earlier today... SUCCESS!!

Fork feels awesome, i filled up 140ml of 7.5 wt oil in each leg for now will make adjustments after a few rides
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